There has long been a need for underinflation indicators and many devices have been sold and others patented to meet this need. While this under inflation is an obvious need, there exists a less obvious need to avoid over inflation. Too high a pressure in a tire not only results in a hard and uncomfortable ride, but also poses safety considerations of blow-outs.
In this present age of energy shortage, particularly in petroleum-based energy sources, the automobiles have been one of the largest users of this form of energy, namely, through the use of gasoline. Efforts are now underway in a variety of areas to improve the mileage of automobiles in order to save gasoline. It has been widely accepted that for an ordinary car, improperly inflated tires can lead to a decrease in mileage per gallon of gasoline. In most instances the direct cause is that an improperly inflated (i.e. not enough pressure) tire leads to more contact area of the tire with the road surface and hence increases friction. Radial tires present a particular problem in that they bulge and seem underinflated at proper tire pressures and they seldom seem to bulge more at low tire pressures.
For most mechanically oriented persons the checking of the tires with a tire gauge once a week or less is a routine and easy matter. Other less mechanically inclined individuals have to rely regularly on other people checking the tire pressures for them. This is normally done at the service stations while these people are buying gasoline. However the proliferation of self-service stations in order to compensate for the sky-rocketing price of gasoline has just about eliminated this regular tire pressure checking service for most gasoline buyers. The end result is that a growing number of people these days are driving with improperly inflated tires most of the time, due to the lack of tire checking service. A simple device is needed at least to alert these people that the tires on their automobiles need pressure. Once they know they can take action to correct the situation.
Although devices exist today for telling people the pressure of their tires the complexity of using them remains a problem for the mechanically less-inclined general public. One of the recent devices, other than the standard tire pressure gauge, is a miniaturized pressure gauge built into a screw-on device tire pressure stem. This device can be screwed into the tire pressure inlet stem and the pressure can then be read off from the miniaturized gauge. While this device eliminates the need to know how to use a standard gauge to read the tire pressure it is still not simple enough in that one still has to learn how to use and read this miniaturized gauge. In view of the size of the gauge it is difficult to read and the accuracy can also be questioned. A more simple and quicker way of checking the tire pressures is clearly desirable at the present time.